NES front loader - Yellow solid screen

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bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

NES front loader - Yellow solid screen

Post by bad_boo »

Hello,

Hope someone could guide me into the right direction.

I have this NES that was working decently. But I tried to do the stereo mod and now I am getting a solid yellow screen.

Image

I have undone all the soldering from the attempted mod, I have disabled the lockout chip, I have changed the 2200 uf cap. Also I have swapped the 72 pin with the other broken NES that I have, and no change.

Then I have turned on the console without the 72 pin hooked up, and still get I same yellow screen. No difference.
Also I can keep pressing reset, and sometimes I get some gray and blue screens.

I saw on another forum that the SN74LS139N chip could be a reason for gray screens. I think its state may not be the best though. But I could try ordering one off ebay and try.....( when I got this console, had some rust problems)
Image


After that, I would be running out of ideas, so any input would be a great help.

Thank you
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: NES front loader - Yellow solid screen

Post by lidnariq »

You've got a lot of corrosion problems on that PCB and it's definitely not helping things. You'll want to clean that up and apply something to slow down future corrosion.

But that said, even with the corrosion, I think that pin on the 74'139 is still connected to the mainboard - you can test with a multimeter - and if it is I don't think it'll be a problem.

Which guide for the stereo mod did you follow? I fear you might have fried the CPU, especially if you're not accustomed to soldering.

My standard advice for this is to check for changing voltages on specific pins on the CPU. If you have a multimeter with a frequency or logic probe, that's easiest, but you can also use a bunch of LEDs and a resistor.

(Check A0 and M2 - https://wiki.nesdev.com/w/index.php/CPU ... escription )
bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

Re: NES front loader - Yellow solid screen

Post by bad_boo »

lidnariq wrote: Fri Oct 09, 2020 5:57 pm You've got a lot of corrosion problems on that PCB and it's definitely not helping things. You'll want to clean that up and apply something to slow down future corrosion.

But that said, even with the corrosion, I think that pin on the 74'139 is still connected to the mainboard - you can test with a multimeter - and if it is I don't think it'll be a problem.

Which guide for the stereo mod did you follow? I fear you might have fried the CPU, especially if you're not accustomed to soldering.

My standard advice for this is to check for changing voltages on specific pins on the CPU. If you have a multimeter with a frequency or logic probe, that's easiest, but you can also use a bunch of LEDs and a resistor.

(Check A0 and M2 - https://wiki.nesdev.com/w/index.php/CPU ... escription )
Thanks so much for your reply.
Yes, that rust has been a problem, but like you said, maybe it is not the main issue as it was working fairly well before.

I followed this guide for the mod: http://www.retrofixes.com/2013/09/nes-s ... -easy.html, But for sure, it was due to my soldering skills that made this issue.

I have a multimeter, I can test what you explained.

Also I think what you say makes sense, could be the CPU. If it is that, is it something I can just change? or would I need a broken donor NES to get it?
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: NES front loader - Yellow solid screen

Post by lidnariq »

You can buy 3rd party clones of the NES's CPU, but let's see what your test results are first.
bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

Re: NES front loader - Yellow solid screen

Post by bad_boo »

Will check that, in that case.
Thank you
hiju123
Posts: 3
Joined: Tue Nov 17, 2020 4:48 pm

Re: NES front loader - Yellow solid screen

Post by hiju123 »

Hi. Did you get the issue sorted out? I have the exact same problem with the solid yellow screen with and without the cartridge. Disabled the lockout chip as well. Still a no go.
[Removed post-widening quote - MOD]
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: NES front loader - Yellow solid screen

Post by lidnariq »

Here's my first steps of trouble-shooting a cantankerous NES:

* Does your TV think the output video is valid? (For example, a solid yellow screen?) If so, this means that you know the 21.5MHz or 26.6MHz clock works, and the PPU at least partially works.

Subsequent steps will require a logic tester of some sort. I favor this simple one, but anything will work.

The next steps are:
* Check if the CPU /RESET pin is high (pin 3)
If /RESET is not high, use one of the various schematics to figure out why.
* Check if the CPU M2 pin (pin 31) is oscillating (i.e. your logic tester should show both high and low, or my "two LEDs" one should light both LEDs)
If /RESET is high, and the 21.5MHz clock is arriving at the CPU (pin 29), and M2 is not oscillating, the CPU is broken.
* Check if the CPU A0 pin (pin 4) is also oscillating.
If things are almost working, A0 will oscillate for a little time and eventually stop at high or low. It will restart when you press the reset button.
If A0 never changes between high and low, the CPU is broken.
If A0 keeps on oscillating, but the PPU never starts drawing a valid picture, then either the CPU's RAM or the PPU could be broken, or much less likely, the 74*139.

Separate tests that can also be useful:
* Does the power LED blink in the standard "failure" way without a cart? Then you know that the 4 MHz clock works, and the CIC lock at least mostly works
* Does the power LED not blink if you have a cartridge in, even if nothing else works? Then you know that the CIC fully works (unless deliberately disabled) and the 74HCU04 mostly works.
bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

Re: NES front loader - Yellow solid screen

Post by bad_boo »

hiju123 wrote: Tue Nov 17, 2020 4:57 pm Hi. Did you get the issue sorted out? I have the exact same problem with the solid yellow screen with and without the cartridge. Disabled the lockout chip as well. Still a no go.
[Removed post-widening quote - MOD]
hi, unfortunately I haven't yet. I left it as it is for now. I will come back to it and post it if I find a solution.
lidnariq wrote: Sun Nov 22, 2020 12:46 am Here's my first steps of trouble-shooting a cantankerous NES:

* Does your TV think the output video is valid? (For example, a solid yellow screen?) If so, this means that you know the 21.5MHz or 26.6MHz clock works, and the PPU at least partially works.

Subsequent steps will require a logic tester of some sort. I favor this simple one, but anything will work.

The next steps are:
* Check if the CPU /RESET pin is high (pin 3)
If /RESET is not high, use one of the various schematics to figure out why.
* Check if the CPU M2 pin (pin 31) is oscillating (i.e. your logic tester should show both high and low, or my "two LEDs" one should light both LEDs)
If /RESET is high, and the 21.5MHz clock is arriving at the CPU (pin 29), and M2 is not oscillating, the CPU is broken.
* Check if the CPU A0 pin (pin 4) is also oscillating.
If things are almost working, A0 will oscillate for a little time and eventually stop at high or low. It will restart when you press the reset button.
If A0 never changes between high and low, the CPU is broken.
If A0 keeps on oscillating, but the PPU never starts drawing a valid picture, then either the CPU's RAM or the PPU could be broken, or much less likely, the 74*139.

Separate tests that can also be useful:
* Does the power LED blink in the standard "failure" way without a cart? Then you know that the 4 MHz clock works, and the CIC lock at least mostly works
* Does the power LED not blink if you have a cartridge in, even if nothing else works? Then you know that the CIC fully works (unless deliberately disabled) and the 74HCU04 mostly works.
Hi, sorry for my late reply. After posting this back in October, my second NES broke down too (just for swapping the 72 pins and stopped working after that). So I got so frustrated with all of this, that I put everything in a bin.

Anyway, I just felt like coming back to it, as I was ordering some capacitors to try out, and found your comment. Thanks for the explanation.
I will try these tests and will come back with the results.

Hopefully I don't get the CPU or PPU broken, as I believe these are hard to replace?
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: NES front loader - Yellow solid screen

Post by lidnariq »

bad_boo wrote: Sun Dec 13, 2020 11:48 am Hopefully I don't get the CPU or PPU broken, as I believe these are hard to replace?
New Old Stock clone CPUs and PPUs exist and are quite affordable, and are good (but not perfect) clones. See my two pages on the wiki:
https://wiki.nesdev.com/w/index.php/Use ... _revisions
https://wiki.nesdev.com/w/index.php/Use ... _revisions
hiju123
Posts: 3
Joined: Tue Nov 17, 2020 4:48 pm

Re: NES front loader - Yellow solid screen

Post by hiju123 »

Any progress on the nes ?



bad_boo wrote: Sun Dec 13, 2020 11:48 am
hiju123 wrote: Tue Nov 17, 2020 4:57 pm Hi. Did you get the issue sorted out? I have the exact same problem with the solid yellow screen with and without the cartridge. Disabled the lockout chip as well. Still a no go.
[Removed post-widening quote - MOD]
hi, unfortunately I haven't yet. I left it as it is for now. I will come back to it and post it if I find a solution.
lidnariq wrote: Sun Nov 22, 2020 12:46 am Here's my first steps of trouble-shooting a cantankerous NES:

* Does your TV think the output video is valid? (For example, a solid yellow screen?) If so, this means that you know the 21.5MHz or 26.6MHz clock works, and the PPU at least partially works.

Subsequent steps will require a logic tester of some sort. I favor this simple one, but anything will work.

The next steps are:
* Check if the CPU /RESET pin is high (pin 3)
If /RESET is not high, use one of the various schematics to figure out why.
* Check if the CPU M2 pin (pin 31) is oscillating (i.e. your logic tester should show both high and low, or my "two LEDs" one should light both LEDs)
If /RESET is high, and the 21.5MHz clock is arriving at the CPU (pin 29), and M2 is not oscillating, the CPU is broken.
* Check if the CPU A0 pin (pin 4) is also oscillating.
If things are almost working, A0 will oscillate for a little time and eventually stop at high or low. It will restart when you press the reset button.
If A0 never changes between high and low, the CPU is broken.
If A0 keeps on oscillating, but the PPU never starts drawing a valid picture, then either the CPU's RAM or the PPU could be broken, or much less likely, the 74*139.

Separate tests that can also be useful:
* Does the power LED blink in the standard "failure" way without a cart? Then you know that the 4 MHz clock works, and the CIC lock at least mostly works
* Does the power LED not blink if you have a cartridge in, even if nothing else works? Then you know that the CIC fully works (unless deliberately disabled) and the 74HCU04 mostly works.
Hi, sorry for my late reply. After posting this back in October, my second NES broke down too (just for swapping the 72 pins and stopped working after that). So I got so frustrated with all of this, that I put everything in a bin.

Anyway, I just felt like coming back to it, as I was ordering some capacitors to try out, and found your comment. Thanks for the explanation.
I will try these tests and will come back with the results.

Hopefully I don't get the CPU or PPU broken, as I believe these are hard to replace?
bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

Re: NES front loader - Yellow solid screen

Post by bad_boo »

lidnariq wrote: Sun Dec 13, 2020 12:45 pm
bad_boo wrote: Sun Dec 13, 2020 11:48 am Hopefully I don't get the CPU or PPU broken, as I believe these are hard to replace?
New Old Stock clone CPUs and PPUs exist and are quite affordable, and are good (but not perfect) clones. See my two pages on the wiki:
https://wiki.nesdev.com/w/index.php/Use ... _revisions
https://wiki.nesdev.com/w/index.php/Use ... _revisions
Thank you. This would be helpful.
I have two NES consoles, as I mentioned above, so I this would be a great backup.
bad_boo
Posts: 6
Joined: Fri Oct 09, 2020 10:17 am

Re: NES front loader - Yellow solid screen

Post by bad_boo »

hiju123 wrote: Tue Dec 29, 2020 8:25 am Any progress on the nes ?
nothing yet.
However the console started working by itself and I was getting video, but it has some issues still.
https://www.reddit.com/r/consolerepair/ ... ise_issue/

I guess this time I will look into the PPU/SRAM correction, as recommended above, but I am not sure if it turns out to a different issue. Will check to see if I am better opening a new thread.
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